The physical environment of a living cell influences its ability to proliferate, metabolize, differentiate and remodel. Living cells specify lineage and express different phenotypic and physical states with extreme responsiveness to stiffness (i.e., shear modulus) of their underlying matrix.
A general consensus is emerging among bioengineers and life scientists that rigid substrates may, in many cases, be inappropriate for assessing cell behaviors. Early efforts to more realistically mimic the tissue environment relied on three dimensional reconstituted biological components that form hydrogels, such as collagen, fibrin, and Matrigel. More recently, synthetic, self-assembling peptide gels (PuraMatrix), alginate sponges (AlgiMatrix), and hyaluronan-derived gels (Glycosan) have become commercially available. However, these methods can be prohibitively costly, technologically impractical, or incompatible with many cell-based high-throughput assays, which are designed with 2-D systems in mind. And while culture in three dimensions is appreciated, in general, these systems do not allow wide control of elasticity. Further, in many cases, cell responses to pharmaceutical compounds and biologics in vitro do not accurately predict in vivo functionality and toxicity.